The long-range objective of the project is to explain the genesis of rhythmic output by the mammalian respiratory oscillator in terms of interactions between brain-stem respiratory neurons. The aim is to deal with three questions: 1) How is the slowly augmenting inspiratory discharge pattern generated? 2) How is the abrupt termination of inspiratory discharge produced? 3) How is the duration of the expiratory phase, together with the abrupt onset of inspiratory discharge, determined? These problems will be studied by analyzing the discharge patterns of brain-stem respiratory neurons in relation to respiratory motor output (e.g., phrenic discharge) under the influence of various forcing inputs (e.g., lung inflation, somatic afferent stimulation). The functional interconnections between different types of respiratory neuron will be deduced by analysis of time relations, especially on a fast time scale, between two or more activities (e.g., discharges of two simultaneously recorded brain-stem respiratory neurons, discharges of both phrenic nerves). The data will be analyzed by the computer methods of triggered signal-averaging, autocorrelation, and crosscorrelation. Certain related problems will also be investigated: 1) the influence on respiratory pattern of tonic inputs originating in forebrain and midbrain systems, especially in relation to arousal mechanisms; 2) the influence of the brain-stem respiratory oscillator on non-respiratory systems, especially those involved in genesis of sympathetic discharge; 3) the postnatal development of the Breuer-Hering reflex.